Timestamps¶

Status: proposed shell helpers for DUNE job scripts. This page does not record a DUNE-wide adoption decision.

Timestamp formats¶

Job scripts in HEP experiments frequently embed timestamps, in log lines, output filenames, and directory tags. Without a shared convention, ad-hoc formats accumulate: colons in filenames, local-time stamps mislabelled as UTC, and inconsistent separators.

There are two distinct use cases, each needing a different format:

A common mistake is %Y-%m-%dT_%H%M%SZ, with a literal underscore after the T. That is not ISO 8601. The canonical separator between date and time is just T, with no extra character.

Always use -u (UTC / Zulu)¶

The Z suffix in both formats is a claim that the timestamp is UTC. Use date -u to make the result independent of the host timezone:

date -u +%Y-%m-%dT%H:%M:%SZ    # correct, UTC
date    +%Y-%m-%dT%H:%M:%SZ    # wrong, local time labelled as UTC

Without -u, these commands use the host timezone, which may differ from UTC.

Proposed shared helpers¶

# Canonical UTC timestamp for log lines (ISO 8601 with colons)
iso_now()      { date -u +%Y-%m-%dT%H:%M:%SZ; }

# Colon-free UTC timestamp safe for filenames and directory tags
iso_now_file() { date -u +%Y%m%dT%H%M%SZ; }

log() { echo "[$(iso_now)] $*"; }
outdir="run_$(iso_now_file)"

Adoption requirements¶

Agree where DUNE job scripts should obtain these helpers and which maintained scripts should use them. A shared worker-setup script for justIN jobs is one candidate; the implementation and owner remain to be agreed.